Northern San Joaquin Valley irrigation districts have sold nearly $140 million worth of water to out-of-district agencies during the last decade. At the same time, they’ve pump nearly 1.5 million acre feet of groundwater – that’s 487 billion gallons – from the region’s aquifers.

Water from the Oakdale Irrigation District is delivered to a rice field in Valley Home. The district sold $4 million worth of water to outsiders last year.
Modesto Bee

Irrigation districts provide water that’s key to agricultural prosperity in the Northern San Joaquin Valley, but some of those districts also have been cashing in on the region’s water resources.

They’ve sold nearly $140 million worth of water to out-of-district agencies during the past decade. At the same time, they’ve pumped nearly 1.5 million acre-feet of groundwater – that’s 487 billion gallons – from the region’s aquifers.

Concerns about falling groundwater levels persuaded Stanislaus County supervisors to outlaw groundwater mining last fall, but their ordinance exempted irrigation districts from the ban.

To gauge how much water those public agencies have been pumping and selling, The Modesto Bee gathered data from irrigation districts throughout the region.

Here’s what The Bee found:

• The Turlock Irrigation District dwarfs all others when it comes to pumping groundwater, sucking up nearly 115,000 acre-feet of it last year alone. But TID didn’t sell a drop of that water to anyone outside its borders.
• The Oakdale Irrigation District sold more than $35 million worth of water to outsiders the past 10 years, including $4 million worth in 2013. Despite having surplus water to sell from its Sierra reservoirs, OID continued to pump its Valley wells.
• The Merced Irrigation District dramatically increased its well pumping last year, despite selling $7.2 million worth of reservoir water to other agencies. It plans to continue pumping and selling water this year.
• The relatively small Patterson and West Stanislaus irrigation districts have sold million of dollars’ worth of surplus Central Valley Project water to agencies like the Westlands and Santa Clara Valley water districts, but they continued to pump groundwater to irrigate their local farms.
• The South San Joaquin Irrigation District sold more than $20 million in reservoir water to outsiders during the decade, while continuing to pump groundwater.
• The Modesto Irrigation District hasn’t pumped much and hasn’t sold any water to outsiders for at least a decade.
• Some water districts, like Del Puerto and Oak Flat, neither pumped groundwater nor sold water outside their districts.

Irrigation district leaders who have sold to outsiders insist they’ve done nothing wrong. They say they’ve always pumped groundwater, even when they weren’t selling water to others.

Some water experts and community leaders, however, question the wisdom of pumping from this region’s declining aquifers before irrigating with water available from reservoirs and other sources of surface water.

“The surface water should not escape the county until we can show people we’re being better stewards of the groundwater,” said Sarge Green, a California Water Institute director who is advising Stanislaus County’s newly formed Water Advisory Committee.

Numerous groundwater experts have warned San Joaquin Valley leaders about seriously falling water tables. The problem is worse in some regions – like eastern Stanislaus and much of Merced County – than in other places, like west of the San Joaquin River.

“In any year, there’s more groundwater going out than there is water going back into the ground. It’s called overdraft,” explained Thomas Harter, a hydrologist who focuses on groundwater management at UC Davis.

The drought may have heightened awareness, but Harter said aquifers are declining even during wet years.

That’s a problem because it’s not only farmers who depend on those aquifers: Virtually every Northern San Joaquin Valley resident drinks groundwater. So if wells run dry – and some small rural ones already have – there could be big trouble for city and country folks alike.

“Groundwater certainly is a finite resource,” Harter warned the Water Advisory Committee at its meeting this week. “You can’t be in the negative forever.”

Districts take no blame

Irrigation district managers acknowledged that eastern Stanislaus and Merced water tables are dropping, but they don’t believe their agencies are to blame. They contend that years of channeling Sierra snowmelt into reservoirs and through their irrigation canals has helped recharge the Valley’s aquifers.

As they see it, when irrigation districts pump groundwater, they’re just recapturing water they previously contributed to the water basin.

But rather than continuing to bring all that Sierra snowmelt to Stanislaus and Merced counties – where it had flowed naturally for thousands of years – several irrigation districts have opted to sell that water for big bucks to other parts of California.

That’s been particularly true for the Merced Irrigation District and the Oakdale Irrigation District.

Merced has collected nearly $56.4 million by selling more than 312,000 acre-feet of water (that’s nearly 102 billion gallons) to outside agencies the past decade.

Last year was a particularly profitable sales year for Merced. It collected more than $7.2 million selling 21,445 acre-feet of water to agencies like Westlands, which irrigates Fresno County farms.

But 2013 also marked a five-year high in groundwater pumping for Merced: It pumped nearly 57,000 acre-feet of water from the aquifer, and it sold that water to local farmers.

The district’s general manager, John Sweigard, said it basically has been a business decision to sell some of the reservoir water rather than distribute all of it to Merced-area farms.

“We used (money from out-of-district water sales) specifically to protect MID’s resources and to help MID’s long-term sustainability,” said Sweigard, referring to his Merced district (not the Modesto Irrigation District, which also calls itself MID). Merced hopes to make an additional $5 million from water sales this year. “The revenue from those water sales helps MID survive.”

Sweigard said his governing board decides in advance how much groundwater the district will pump, and “if we hadn’t sold water to Westlands, there would have been no change in the amount of groundwater we pumped.”

Oakdale leaders also justify their decisions regarding how much Sierra water to sell and how much groundwater to pump. Since 2004, OID has transferred 382,408 acre-feet of water outside its borders and collected more than $35.3 million for it.

That cash has helped Oakdale modernize and replace its infrastructure, boost its reserves and keep its irrigation water rates the lowest in the region.

Despite having extra reservoir water to sell, however, Oakdale has continued to pump groundwater. That was particularly true in 2013.

In 2012, when Oakdale didn’t sell any water outside its district, it pumped 6,634 acre-feet of groundwater. Last year, after it sold 40,000 acre-feet of water to Westlands for $4 million, it pumped 10,112 acre-feet of groundwater. That was a one-year increase of 52 percent.

That increase in pumping had nothing to do with the sale of surface water, according to Oakdale’s general manager, Steve Knell.

“OID always pumps groundwater whether we have (out-of-district water) transfers or not,” Knell said. By his calculations, what his district pumped last year was within a “standard deviation” of what it historically has pumped.

Knell acknowledged his eastern Stanislaus region’s water table is declining, but he said, “Year over year, OID and the irrigation practices of our farmers and district provide a net positive return of water to the aquifer.”

Why groundwater levels continue to decline there, Knell said he does not know, but “it would be our opinion that influences outside our control are having an impact.”

‘Let’s keep it here’

Stanislaus County Supervisor Terry Withrow, however, expressed concern about local irrigation districts shipping water outside the region rather than allowing it to flow into the county.

Withrow said that while irrigation districts were exempted from Stanislaus’ law prohibiting groundwater mining, they can’t just do whatever they want.

If an irrigation district’s water sale “is not part of a sound water management plan, then it’s prohibited and they lose that exemption,” Withrow assured. Rather than continuing to sell surplus water to farmers in other counties, Withrow said, “I would hope it is shared within this county instead. Let’s keep it here.”

But shipping water south to well-financed agencies like Westlands sometimes is much easier than transferring it to rural portions of Stanislaus that don’t have canal systems.

That’s been the case for the Patterson and West Stanislaus irrigation districts, both of which have been selling surplus Central Valley Project water to Westlands and other agencies connected to that massive federally operated canal system.

Patterson made more from out-of-district water sales last year that any other Stanislaus irrigation district: $4.4 million. That’s impressive, considering the county’s No. 2 seller, Oakdale, is more than six times larger in size than Patterson.

Like Oakdale and Merced, Patterson used sales proceeds to pay for various operational costs, reserves and capital improvement projects.

Westlands has been one of Patterson’s best customers, having paid more than $6.4 million total to purchase water each of the past 10 years.

Throughout that decade, meanwhile, Patterson pumped groundwater and diverted San Joaquin River water to help meet its farmers’ needs.

“We use groundwater primarily in areas where we have flow restrictions like where we have more demand than we have room in the canals,” explained Patterson’s manager, Peter Rietkerk.

Rietkerk said he doesn’t see any problem with pumping groundwater while selling surface water, in part because aquifers in western Stanislaus haven’t declined. “The water levels have not changed much, if any, in recent history,” he said.

Groundwater expert Green didn’t disagree with that, but he said more research needs to be done.

“The original intent of providing Central Valley Project water was to get people off of groundwater,” said Green, explaining how the severe overdrafting of San Joaquin Valley aquifers decades ago had caused the ground’s surface to sink.

That’s called subsidence, and recent studies show it’s starting to happen again in parts of southern Merced and northern Madera counties.

In his presentation to Stanislaus’ Water Advisory Committee, UC hydrologist Harter showed how pumping groundwater from one location can ultimately lower the water table in locations many miles away.

Figuring out the complex details of how groundwater flows in the Northern San Joaquin Valley is something most experts agree needs to be done.

“How much can you safely pump before you damage the aquifer?” Green asked. He said that’s a question irrigation districts need to answer before they sell their surface water.

And before making a business decision to sell water outside their boundaries, Green said, irrigation districts need to determine this: “Does that serve the greater public good?”

“We’re on the cusp of major problems if we don’t address (falling groundwater levels),” Green warned. “We’ve got to get better at long-term management. If we don’t, the state is going to intercede.”